1. Field of the Invention
The present invention relates to a mobile communication system and a resource management method thereof, and more particularly to a mobile communication system and a resource management method thereof suitable for performing an inter-station handoff extending over a plurality of switching centers.
In the mobile communication system, the inter-station handoff is frequently performed because the number of switching centers has greatly increased with the increasing of subscribers and the enlarging of communication areas.
2. Description of the Related Art
In a conventional mobile communication system, a handoff is performed, which handoff involves switching a connection to different base stations one after another with movement of a mobile station. In particular, in a Code Division Multiple Access (CDMA) which is different from a Frequency-Division Multiple Access (FDMA), a mobile station can communicate with a plurality of base stations in the same frequency. For this reason, while communicating with a base station, the mobile station can communicate with a next (target) base station. Further, the mobile station carries out a soft diversity while maintaining communication with both of the above-mentioned base stations so as to perform a seamless handoff without a short transmission interruption, namely, a soft handoff.
Performing such a handoff may bring about a change in resources of a switching center. The resources are information about a connection of a mobile station which generates a call control and writes the call control into a memory in a call. The resources contain anchor information as fixed information and drift information as variable information corresponding to the anchor information of the mobile station. The handoff may bring about a change in the drift information, such that an abnormality is found, the abnormality being, for example, that a resource to be released is not released or has become an abnormal link.
In a conventional mobile communication system and resource management method thereof, as shown in FIG. 1, a communication between two mobile stations (MS) 21, 22 is carried out through two base station systems (BSS) 12, 14 which are connected to a switching system 10. When a resource A (drift information of a calling side) Is found to be abnormal due to, for example, a long-duration call, a maintainer inputs a route trace command for the resource A to confirm normality of resources B, C and D which are in serial connection in the long-duration call. The route trace functions to trace resources of a call control generated in a calling connection and written into a memory, so as to confirm whether the call is correctly connected or not.
As shown in FIG. 2, in a case in which the resource A is detected as abnormal due to floating (the resource is not being effectively used), the maintainer inputs the route trace command for the abnormal resource A. When the resource A is detected as not being connected to any resource, a process of releasing the resource A is carried out.
According to movement of a mobile station, an inter-station handoff may extend over a plurality of switching centers.
In another conventional mobile communication system and resource management method thereof, as shown in FIG. 3, a communication between two mobile stations (MS) 21, 22 is carried out through two base station systems (BSS) 12, 15 which are connected respectively to two switching systems 10, 11. When a resource A (drift information of a calling side) is detected as abnormal due to, for example, a long-duration call, a maintainer inputs in the switching system 10 a route trace command for the abnormal resource A to confirm normality of resources B, C, D which are in serial connection. In the switching system 10 into which the route trace command has been inputted, the resource B can be detected. However, the route trace cannot be carried out in the switching system 11. If the maintainer does not separately input the route trace command into the switching system 11, normality of the resources C and D cannot be confirmed. Thus, normality of the resources A, B, C and D which have been used in the long-duration call cannot be confirmed automatically by one route trace command.
As shown in FIG. 4, in a case in which an abnormal resource is detected due to floating of the resource C in the switching system 11, even though the maintainer inputs the route trace command into the switching system 10, since the resources A and B are normally connected to each other in the switching system 10, the resources A, B and C cannot be released.
It is a general object of the present invention to provide a mobile communication system and resource management method thereof, in which the above disadvantages are eliminated.
A more specific object of the present invention is to provide a mobile communication system and resource management method thereof, in which a route trace can be automatically carried out among a plurality of switching centers when a call control of a handoff extends over the switching centers.
The above object of the present invention is achieved by a mobile communication system for performing an inter-station handoff extending over a plurality of switching centers, the mobile communication system comprising: a route trace portion which actuates a route trace so as to trace resources of call control in a local station, an inter-station checking functional portion in which the resources are checked as to whether or not the resource becomes an inter-station resource by the inter-station handoff, and an inter-station communication portion which notifies a remote station to execute a route trace when the resource is the inter-station resource and receives a result of the route trace from the remote station.
Thus, the resource of the call control is route-traced in the local station and is checked as to whether the resource becomes the inter-station resource by the inter-station handoff. When the resource is the inter-station resource, the remote station is notified to execute a route trace and transmits a result of the route trace to the local station. Hence, when the resources of the call control are the inter-station resources, a route trace automatically extending over a plurality of switching centers can be automatically carried out.
The mobile communication system may further comprise a resource releasing portion which releases an abnormal resource detected by the route trace result.
Thus, since the abnormal resource detected by the route trace result is released, the abnormal resource can be automatically released in the local station.
The mobile communication system may be configured so that: the resource releasing portion notifies the remote station through the inter-station communication portion so as to release an abnormal resource detected by the route trace result from the remote station.
Thus, since the remote station is notified to release the abnormal resource detected by the route trace result from the remote station, the abnormal resource in the remote station can be automatically released in a case of inter-station call control.
The mobile communication system may further comprise a resource checking portion which checks the resource and a route trace actuating portion which actuates the route trace if the resource is checked as being abnormal.
Thus, since the resource is checked and the route trace is actuated if the resource is checked as being abnormal, when the abnormality is found, all of the abnormal resources in the local and remote stations can be automatically released.
Further, the above object of the present invention is achieved by a resource management method of the mobile communication system according to the present invention, comprising the steps of: a) actuating a route trace so as to trace resources of call control in a local station, b) checking whether or not each of the resources becomes an inter-station resource by the inter-station handoff; and c) notifying a remote station to execute a route trace when the resource is the inter-station resource and receiving a result of the route trace from the remote station.
Thus, the resource of the call control is route-traced in the local station and is checked as to whether the resource becomes the inter-station resource by the inter-station handoff. When the resource is the inter-station resource, the remote station is notified to execute a route trace and transmits a result of the route trace to the local station. Hence, when the resources of the call control are the inter-station resources, a route trace automatically extending over a plurality of switching centers can be automatically carried out.
The resource management method further comprises the step of d) releasing an abnormal resource detected by the route trace result.
Thus, since the abnormal resource detected by the route trace result is released, the abnormal resource can be automatically released in the local station.
The resource management method further comprises the step of e) signaling the remote station so as to release an abnormal resource detected by the route trace result from the remote station.
Thus, since the remote station is notified to release the abnormal resource detected by the route trace result from the remote station, the abnormal resource in the remote station can be automatically released in a case of inter-station call control.
The resource management method further comprises the step of f) checking whether or not the resource is abnormal and actuating a route trace in the local station if the resource is abnormal.
Thus, since the resource is checked and the route trace is actuated if the resource is checked as being abnormal, when abnormality is found, all of the abnormal resources in the local and remote stations can be automatically released.